Wellbores are drilled into the Earth's formation to recover deposits of hydrocarbons and other desirable materials trapped in the formations below. Typically, a wellbore is drilled by connecting a drill bit to the lower end of a series of coupled sections of tubular pipe known as a drillstring. Drilling fluids, or mud, are pumped down through a central bore of the drillstring and exit through ports located at the drill bit. The drilling fluids act to lubricate and cool the drill bit, to carry cuttings back to the surface, and to establish sufficient hydrostatic “head” to prevent formation fluids from “blowing out” the borehole once they are reached.
To sample and test fluids, such as deposits of hydrocarbons and other desirable materials trapped in the formations, a formation tester is typically deployed in the wellbore drilled through the formations. Various formation fluid testers for wireline and/or logging-while-drilling applications are known in the art, such as those described in U.S. Pat. Nos. 4,860,581, 4,936,139, and 7,458,419. The entireties of these patents are hereby incorporated herein.
One characteristic of interest of a formation fluid may be the electrical resistivity of the fluid. Resistivity of fluids passing through a flow line of the formation fluid testers may be measured. Sensors configured to measure the resistivity of fluids within the flow line include, for example, those described in U.S. Pat. No. 7,183,778, the entirety of which is incorporated herein by reference.